Communication system, communication control method, and mobility management node

ABSTRACT

A node on a core network, in accordance with a connection state of a terminal, releases a transmission path resource which is made unnecessary due to LIPA (Local IP access) or SIPTO (Selected IP traffic offload) connection configuration.

TECHNICAL FIELD Cross-Reference to Related Applications

The present application asserts priority rights based on JP PatentApplication 2009-217755 filed in Japan on Sep. 18, 2009 and on JP PatentApplication No. 2009-256493 filed on Nov. 9, 2009. The total contents ofdisclosures of these patent applications of the senior filing dates areto be incorporated by reference into the present Application.

This invention relates to a communication system and, more particularly,to a system and a method for optimizing transmission path resources.

BACKGROUND

With the increase in the volume of user communication, in 3GPP (ThirdGeneration Partnership Project) standardization, a study is currentlybeing made of the technique that enables a terminal (User Equipment: UE)to access to an external network directly from a radio access network ofa service area in which the terminal stays, without capturing a usertraffic into the EPC (Evolved Packet Core), as in

-   -   LIPA (Local IP access); or    -   SIPTO (Selected IP traffic offload). It is noted that the        LIPA/SIPTO system provides a mechanism of directly connecting a        radio base station, a radio control apparatus or a simple        structure type radio apparatus, such as Femto base station, to        an external network.

SUMMARY

The following describes an analysis by the present inventors. Thespecial access methods, such as LIPA or SISTO, and ordinary accessmethods, may coexist in future. Under such situation, it may becomenecessary to efficiently exploit network resources.

FIG. 1 shows a connection network configuration of LTE (Long TermEvolution)/EPC. A terminal (UE) 1 communicates with a radio station(evolved Node-B: eNB) 2 via a radio transmission path 7. When theterminal (UE) 1 is engaged in communication, connection is set up via aradio transmission path 7, an S1 transmission path 8 and an S5transmission path 9, thus allowing the terminal (UE) 1 to havecommunication with the service network (Service Network) 6. At thistime, to secure the communication quality, such as QoS (Quality ofService), each apparatus or component secures transmission pathresources, depending on services to be provided.

An MME (Mobility Management Entity) 3 of FIG. 1 is a control node thatmanages the mobility and that takes part in bearer activation anddeactivation. For example, the MME performs S-GW selection for the UE ata time point of initial attachment of the UE and intra-LTE handover,while also performing user authentication in conjunction with an HSS(Home Subscriber Server), not shown.

The S-GW (Serving Gateway) 4 performs routing of a user data packet toforward the user data packet. The S-GW 4 also operates as a mobilityanchor for a user plane during handover between eNBs, and as a mobilityanchor for the LTE and other 3GPP systems. A P-GW (PDN (Packet DataNetwork)-Gateway) 5 connects the EPC to the service network 6 which isan external packet network.

FIG. 2 is a diagram for illustrating the problem to be solved by thepresent invention. Referring to FIG. 2, there is shown a networkconfiguration for directly accessing from a radio access network (RAN)to an external network (Internet/Cooperate network). In theconfiguration shown in FIG. 2, a packet is directly transferred from theradio access network via an LPGW (Local Packet data network Gateway) tothe external network. Hence, no packet flows on the S1 transmission pathor on the S5 transmission path, even though the terminal (UE) isactually having communication. In FIG. 2, the eNB is drawn as unitedwith the LPGW (Local PDN GW) to transfer a packet from the radio accessnetwork directly to outside or from the external network directly to theradio access network.

In the configuration of FIG. 2, as a derivative of the usual LTE/EPCconnection configuration, the procedure for transmission path setup isthe same as that of the ordinary LTE/EPC from the standpoint ofachieving common processing.

Thus, in the configuration of FIG. 2, it is a problem to make optimumexploitation of resources of the S1 transmission path and the S5transmission path, in short, to optimize the transmission path resourcemanaged by the S-GW.

Since with LIPA/SIPTO connection, entire user traffics are connectedfrom a LIPA/SIPTO compatible apparatus directly to an external network,that is, not via an operator's network, it is not necessary for theoperator to provide network resources required to implement usercommunication, thereby providing a significant cost merit. However,since it is presupposed that a subscriber is moving from the LIPA/SIPTOcompatible apparatus to other base station, resources needed for normalconnection with an external network are allocated in an operator network(EPC(Evolved Packet Core) network). It is thus desired in the EPC forLIPA/SIPTO access to enable optimizing a GBR (Guaranteed Bit Rate)transmission path to secure the cost merit of LIPA/SIPTO connection tothe maximum extent possible.

It is therefore an object of the present invention to provide a systemand a method that will enable optimizing the use of transmissionresources in mobile communication.

It is another object of the present invention to provide a system and amethod that will enable optimizing the GBR (guaranteed bit rate)transmission path in the EPC for LIPA/SIPTO access.

According to the present invention, unneeded resources are released inmobile communication, depending on the connection configuration, such asto optimize the use of transmission path resources. According to thepresent invention, there is provided a communication method in which anode on a core network, in accordance with a connection state of aterminal, releases a transmission path resource which is madeunnecessary due to LIPA (Local IP access) or SIPTO (Selected IP trafficoffload) connection configuration.

According to the present invention, there is provided a system in whicha core network, when recognizing LIPA/SIPTO connection, captures minimumnecessary resources. According to the present invention, there isprovided a communication system, wherein a node on a core network, inaccordance with a connection state of a terminal, releases atransmission path resource which is made unnecessary due to LIPA (LocalIP access) or SIPTO (Selected IP traffic offload) connectionconfiguration. The communication system is connected to an externalpacket network without catching an interface resource between a radioaccess network and the core network, and provides a resource to theother interface installed in the core network. More specifically, the S1interface interconnecting the radio control network and the core networkis controlled so as not to be provided with a resource. S5/S8 interfaceneeded in a core network is controlled so that it is supplied withminimum necessary resources.

According to the present invention, the terminal connects directly fromthe radio access network to the external packet network, withoutcatching an interface resource between the radio access network and thecore network, such as to provide a resource to the other interface inthe core network.

According to the present invention, use of a transmission path resourcemay be optimized.

According to the present invention, a GBR (guaranteed bit rate)transmission path in the EPC for LIPA/SIPTO access may be optimized tosecure cost merit of LIPA/SIPTO connection to the utmost extentpossible.

Still other features and advantages of the present invention will becomereadily apparent to those skilled in this art from the followingdetailed description in conjunction with the accompanying drawingswherein only exemplary embodiments of the invention are shown anddescribed, simply by way of illustration of the best mode contemplatedof carrying out this invention. As will be realized, the invention iscapable of other and different embodiments, and its several details arecapable of modifications in various obvious respects, all withoutdeparting from the invention. Accordingly, the drawing and descriptionare to be regarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of an LTE/EPC mobilenetwork.

FIG. 2 is a diagram showing a network configuration of direct connectionfrom the radio access (Radio Access) network to outside.

FIG. 3 is a sequence diagram showing a sequence of optimizing a S5transmission path in an exemplary embodiment 1 of the present invention.

FIG. 4 is a diagram for illustrating the selection of contents ofnotification in an MME in the exemplary embodiment 1 of the presentinvention.

FIG. 5 is a diagram showing an example of securing resources in theexemplary embodiment 1 of the present invention.

FIG. 6 is a diagram showing a transmission path in an exemplaryembodiment 2 of the present invention, with a terminal in an Idle state.

FIG. 7 is a sequence diagram showing a procedure of optimizing an S5transmission path (S5 GTPv2) in the exemplary embodiment 2 of thepresent invention.

FIG. 8 is a sequence diagram showing a procedure of optimizing an S5transmission path (S5 MPIV) in a modification of the exemplaryembodiment 2 of the present invention.

FIG. 9 is a diagram showing a 3GPP mobile network in an exemplaryembodiment 3 of the present invention.

FIG. 10 is a diagram showing a transmission path in the exemplaryembodiment 3 of the present invention, with a terminal in Idle state.

FIG. 11 is a sequence diagram showing an optimizing procedure of an S5transmission path (S5 GTPv2) in the exemplary embodiment 3 of thepresent invention.

FIG. 12 is a diagram showing a network configuration at the time ofconnection from UTRAN to EPC in an exemplary embodiment 4 of the presentinvention.

FIG. 13 is a diagram showing a transmission path at the time ofconnection from UTRAN to EPC in the exemplary embodiment 4 of thepresent invention, with the terminal in an Idle state.

FIG. 14 is a diagram showing a typical LIPA/SIPTO connection model withthe UE in ECM-CONENCTED mode.

FIG. 15 is a diagram showing a typical paging procedure to the UE inECM-CONENCTED mode.

FIG. 16 is a sequence diagram illustrating signaling flow in anexemplary embodiment of the present invention.

FIG. 17 is a sequence diagram illustrating signaling flow in anexemplary embodiment 6 of the present invention.

FIG. 18 is a sequence diagram illustrating signaling flow in theexemplary embodiment 6 of the present invention.

PREFERRED MODES

The following describes exemplary embodiments of the present invention.According to the present invention, when a transmission path is set up,an MME (mobility management entity) notifies an S-GW (Serving Gateway)of the connection configuration of a terminal (UE). The S-GW accordinglysecures transmission path resources in a proper manner to optimizetransmission path resources.

In an exemplary embodiment of the present invention, a base station(eNB) informs the MME, at the time of connection setup of thetransmission path between the base station and the mobility managemententity (MME), about whether or not the base station has the ability totransfer a packet directly from a radio access network to an externalnetwork. In response to a request for connection setup from the terminal(UE) to the base station (eNB), the MME selects the connectionconfiguration to be notified to the S-GW, based a network as adestination of connection specified in the request for connection setupand the capability information of the base station. The MME notifies theS-GW of the connection configuration. The S-GW secures at least theresources of transmission paths to which the S-GW connects, and releasesunneeded transmission path resources, in accordance with the connectionconfiguration notified by the MMW.

In another exemplary embodiment of the present invention, the S-GWnotifies the state of connection of the S-GW to a P-GW (PDN Gateway)connecting to an external packet network, based on the connectionconfiguration notified. The P-GW and the S-GW perform the optimizationof at least transmission path resources between the P-GW and the S-GWbased on the connection configuration notified.

In another exemplary embodiment of the present invention, a contextreleasing request by the terminal which is in a non-communicating statemay be sent from the base station to the MME. The MME may then requestthe S-GW to remove the information regarding the transmission pathbetween the MME and the base station. The MME at this time may append tothe removal request a connection state that the UE is in thenon-communicating state, and may send the resulting signal to the S-GW.The S-GW may then notify to the P-GW that the terminal is in anon-communicating state. The S-GW and the P-GW may then optimize thetransmission path resource already secured.

In another exemplary embodiment of the present invention, an SGSN(Serving GPRS Support Node) may notify the connection state to a GGSN(Gateway GPRS Support Node). The GGSN may then optimize the transmissionpath resource between the GGSN and the SGSN based on the connectionstate notified.

FIG. 2 shows a network configuration of directly accessing from a radioaccess network to an external network. Referring to FIG. 2, the eNB isunited with an LPGW (Local PDN GW) and has the function of directlytransferring a packet from the radio access (Radio Access) network tooutside and from the external network to the radio access (Radio Access)network.

Exemplary Embodiment 1

FIG. 3 is a diagram for illustrating a sequence for optimizing an S5transmission path in one exemplary embodiment of the present invention.Referring to FIG. 3, there are shown a procedure for S1 setup (S1 Setup)and a procedure for registering a terminal in a network and for settingup a transmission path.

1) Ability Notification at the Time of Connection Setup

An eNB sets up connection by setup of S1 as an interface between the eNBand an MME (S1 Setup). At the same time, the eNB appends to a normalsignal the information on whether or not the eNB has the ability todirectly transfer a packet from the radio access network to the externalnetwork, and sends the signal with the capability information to the MME(notification of the ability).

The MME receives the notification and maintains the eNB's ability. An S1setup response (S1 Setup Response) is sent from the MME to the eNB.

2) Attach Request (Attach Request)

The registration in the network and a connection setup request (AttachRequest) are sent from the terminal (UE) to the eNB. The eNB notifiesthe MME of the connection setup request (Attach Request).

The MME receives the connection setup request (Attach Request) from theeNB, and sends an authentication information request (AuthenticationInformation Request) to an HSS (Home Subscriber Server) that manages theservice profile information. The MME receives an authenticationinformation answer (Authentication Information Answer) from the HHS andsends an authentication request (Authentication Request) to the UE toreceive an authentication response (Authentication Response) from theUE.

3) Selection of Contents of Notification

The MME performs the authentication (Authentication) and then selects,as shown in FIG. 4, the connection configuration to be notified to theS-GW, from the connection destination network, specified in theconnection setup request, and from the ability of the eNB received in1).

Referring to FIG. 4, in case the PDN is the Internet or the Local Access(YES of step S1), and the eNB is directly connectable to the externalnetwork (YES of step S2), the MME notifies the S-GW of direct connectionto outside, as the connection configuration (step S4). If the results ofdecisions at steps S1 and S3 are NO, the MME notifies the S-GW ofdefault as the connection configuration (step S3).

4) Notification of Connection Configuration

The MME appends the connection configuration, selected in the procedureof FIG. 4, to the normal request for transmission path setup, andnotifies it to the S-GW. That is, the MME notifies the connectionconfiguration in a create session request (Create Session Request).

On receiving the create session request (Create Session Request) fromthe MME, the S-GW sends the create session request (Create SessionRequest) to the LPGW. On receiving the create session request (CreateSession Request) from the LPGW, the S-GW returns a response (CreateSession Response) to the MME.

The MME notifies the eNB of initial context setup (Initial ContextSetup), and the eNB transmits attach accept (Attach Accept) in responseto an attach request (Attach Request) from the terminal of 2).

The eNB sends to the MME an initial context response (Initial ContextSetup Response) responsive to the initial context setup (Initial ContextSetup) from the MME, which MME then sends a modify bearer request(Modify Bearer Request) to the S-GW.

5) In finally completing the connection procedure, the S-GW securesresources of the S1 transmission path and the S5 transmission path,taking the connection configuration into account (transmission pathoptimization of 5) of FIG. 3), as shown in FIG. 5.

In the Example shown in FIG. 5, there are a direct external connection,idle state and a normal state, as bearer types.

As for GBR (Guaranteed Bit Rate), no bandwidth is secured for the directexternal connection, a minimum bandwidth is secured for the idle stateand a bandwidth requested is secured for the normal state.

As for the Non-GBR (Non-Guaranteed Bit Rate), no bandwidth is securedfor any of the direct external connection, idle state or the normalstate.

In case connection is made directly from the radio access network to theexternal network, and the connection services are those that guaranteethe bandwidth, the S-GW resources, normally necessary to secure, do nothave to be secured (GBR, Non-GBR: No bandwidth guaranteed). Thecorresponding communication path resources may be allocated to otherconnections, thus optimizing network resources.

Exemplary Embodiment 2

The following describes an exemplary embodiment 2 of the presentinvention. FIG. 6 shows a state in which a terminal (UE) performsregistration to a network (Attach) and, after securing a transmissionpath, the terminal is in an idle (Idle) state, that is, in anon-transmitting state. At this time, the resources of the radiotransmission path as well as those of the S1 transmission path arereleased. Note that, during the idle (Idle) state, the UE is in a powersupply saving state and no packet is transmitted or received. During theidle state, no context of the terminal (UE) is stored in the eNB.However, even in such a state, in which no transmission packet flows onthe S5 transmission path, resources are being secured. It is necessaryto make optimum use of these resources.

FIG. 7 shows the procedure for releasing the S1 transmission path incase the GTPv2 (GPRS (General Packet radio Service) Tunneling Protocol)protocol is applied to the S5 interface, with the UE in the idle state(in non-communicating state). The following describes the procedure ofreleasing the S1 transmission path, with reference to FIG. 7. A UEcontext release request (UE Context Release Request) is sent from theeNB to the MME.

1) Notification of Connection State

On receiving the UE context release request (UE Context Release Request)from the eNB, the MME sends to the S-GW a modify bearer request (ModifyBearer Request) that requests deletion of the information regarding theS1 transmission path. At this time, the MME appends to the usualdeletion request a connection state that the UE is in non-communicatingstate, and sends the resulting signal to the S-GW.

2) Notification of the Connection State

On receiving the modify bearer request (Modify Bearer Request) from theMME, the S-GW notifies to a P-GW that the terminal (UE) becomes to be ina non-communicating state.

3) S5 Re-Optimization

The S-GW and the P-SW perform optimization of the resources of the S5transmission path, already secured, depending on conditions, as shown inFIG. 5.

The S-GW sends a response (Modify Bearer Response) to the MME. The MMEsends a UE context release command (UE Context Release Command) to theeNB.

The eNB sends a radio resource control connection release (RRC (RadioResource Control) Connection Release) to the UE. Thereafter, the eNBsends to the MME a UE context release complete (UE Context ReleaseComplete). This releases S1 transmission path/radio transmission pathresources.

The following describes a modification of the present exemplaryembodiment. FIG. 8 shows a procedure which is the same as that in casePMIP (Proxy Mobile IP) protocol is applied to the S5 interface. A UEcontext release request (UE Context Release Request) is sent from theeNB to the MME.

1) Notification of Connection State

On receiving the UE context release request (UE Context Release Request)from the eNB, the MME requests the S-GW to delete the informationregarding the S1 transmission path (Modify Bearer Request). At thistime, the MME appends to the normal request for deletion a connectionstate that the UE is in the non-communicating state, and sends theresulting signal to the S-GW.

2) Notification of Connection State

On receiving the modify bearer request (Modify Bearer Request) from theMME, the S-GW notifies to the P-GW, by the signal PMIP, that the UE hasfallen into the non-communicating state.

3) S5 Optimization

The P-GW and the S-GW perform optimization of the S5 transmission pathresources already acquired. The procedure following this is the same asthat shown in FIG. 7 and hence the corresponding explanation isdispensed with.

Exemplary Embodiment 3

The following describes a third exemplary embodiment of the presentinvention. FIG. 9 shows a network configuration to which a 3G (thirdgeneration) mobile communication is applied. When a terminal (UE) 1′ isengaged in communication, a radio transmission path 14, a lutransmission path 15 between RNC (Radio Network Controller)/NB (Node B)and SGSN (Serving GPRS Support Node) and a Gn transmission path 16between SGSN and GGSN (Gateway GPRS Support Node) are set up, as shownin FIG. 9, thus allowing the terminal (UE) 1 to have communication witha service network (Service Network) 6′ as an external network. Therespective apparatuses secure transmission path resources to securecommunication quality, such as QoS (Quality of Service), depending onservices rendered.

FIG. 10 shows a state in which the terminal (UE) has registered to anetwork and, after securing a transmission path, becomes to be in anidle state (non-transmitting state). At this time, the resources of theradio transmission path and the lu transmission path are released.However, even in such case, resources are being secured on the lutransmission path 16, even though no communication packet flows. It isnecessary to make optimal use of these resources.

FIG. 11 shows the procedure for releasing the lu transmission path, withthe terminal (UE) shown in FIG. 10 in the idle state (non-transmittingstate).

1) Release Request (Release Request)

The RNC requests the SGSN to delete the information regarding the lutransmission path.

2) Notification of Connection State (Update PDP Context Request)

Using a signal requesting to change the transmission path, the SGSNnotifies to the GGSN that the UE becomes to be in a non-communicatingstate.

3) Optimizing Gn

The SGSN and the GGSN perform optimization of Gn transmission pathresources for the UE that has fallen into the non-communicating state.On receiving a response (Update PDP context Response) from the GGSN thatperformed optimization of the Gn transmission path resources, the SGSNperforms optimization of the Gn transmission path resources. The SGSNthen transmits a lu release command (lu Release Command) to the RNC/NB.The RNC/NB then disconnects the radio transmission path for UE andreturns a lu release complete (lu Release Complete) to the SGSN. As aresult, the radio transmission path between the UE and RNC/NB and the lutransmission path between RNC/NB and SGSN are released.

Exemplary Embodiment 4

The following describes a fourth exemplary embodiment of the presentinvention. FIG. 12 is a diagram illustrating the present exemplaryembodiment. Referring to FIG. 12, there is shown an ordinary connectionnetwork configuration from the 3GPP (UTRAN (UMTS (Universal MobileTelecommunication System) Terrestrial Radio Access Network)) to the EPC.

When the terminal (UE) 1′ is engaged in communication, a radiotransmission path 14, a lu transmission path 15, an S4 transmission path10 and an S5 transmission path 9 are set up to allow the terminal 1′ tocommunicate with a service network 6, as shown in FIG. 12. At this time,the respective apparatuses secure transmission path resources to providefor the communication quality, such as QoS, depending on servicesrendered.

FIG. 13 shows a state in which the terminal (UE) 1′ has registered tothe network and secured a transmission path, after which the terminalhas fallen into an idle state (non-communicating state).

At this time, the resources of the radio transmission path and the lutransmission path are released. However, even in such case, resourcesare being secured on the S4 communication path 10 between the SGSN andS-GW and on the S5 communication path 9 between the S-GW and the P-GW,even though no communication packet flows over these transmission paths.Note that SGSN connects to RNC 11 and S-GW 4 via a lu transmission path15 and the S4 transmission path 10, respectively, while also connectingto the MME.

Even in such a case, the resources of the S4 transmission path and theS5 transmission path 5 may be optimized by notifying the respectiveapparatuses of the communication state of the terminal (UE) inaccordance with the present invention.

It is possible to combine the above described exemplary embodiments in adesired manner. The present invention may, of course, be applied toroaming (connection among different service providers). In the case ofthe roaming (connection among different service providers), the abovementioned s5 transmission path is called an S8 transmission path.

Exemplary Embodiment 5

According to the present invention, the GBR (Guaranteed Bit Rate)transmission path is enabled to be optimized in the EPC for LIPA/SIPTOaccessing.

According to the present invention, there is provided a communicationsystem in which a core network on recognition of LIPA/SIPTO connectioncaptures the necessary minimum resources. The communication systemaccording to the present invention directly connects to an externalnetwork, without acquiring (capturing) the resources of interfacesbetween the radio control network and the core network (EPC network),thus providing the resources to other interfaces installed in the corenetwork. No resources are assigned to the S1 interface that connectsbetween the radio control network and the core network. The S5/S8interface needed in the core network is controlled so as to be suppliedwith necessary minimum resources.

This invention may be applied to a large number of solutions forLIPA/SIPTO communication captured in TR23.8xy (Local IP Access andSelected IP Traffic Offload).

In the following, UE(User Equipment) is assumed to be in ECM-CONENCTEDmode. FIG. 14 illustrates the typical LIPA/SIPTO connection model withthe connected mode UE. The LP-GW (Local PDN Gateway) can be co-locatedwith the (H)eNB or logically separated depending on the solution.

As shown in FIG. 14, the common issue we can see is that the assigned S1bearer and S5/S8 bearer are not used for traffic that is broken out atthe (H)eNB. In other words, the resources allocated for the S1 bearerand S5/S8 bearer may be wasted for the LIPA/SIPTO connection. This canhappen since entirety of user traffics (i.e., user traffic between a UEand a service network) go through the local P-GW(Local PDN Gateway)located within or close to the (H)eNB and the EPC user plane nodes,i.e., the S-GW(Serving Gateway) (and possibly P-GW depending on thesolution), is not involved in such LIPA/SIPTO traffic.

The S1 bearer is not used for LIPA/SIPTO connection during theECM-CONNECTED mode.

The S5/S8 bearer is not used for LIPA/SIPTO connection during theECM-CONNECTED mode.

This is not major issue for non-GBR bearers since there is not muchresources consumed in EPC. However, for the GBR bearers, the inefficientuse of resources would be a major issue for 3G operators.

Next, UE is assumed to be in ECM-IDLE mode. FIG. 2 illustrates a casewhere the DL(Down Link) packet arrives to the LP-GW while UE is in theECM-IDLE mode.

Since there is some possibility that the UE is located in the trackingarea, the paging has to be performed to all Macro eNBs and HeNBs thatare located in the same tracking area. It means that the S-GW andMME(Mobility Management Entity) are involved for the paging procedure asthe same way as usual case as specified in the TS 23.401/TS 23.060. Inthis logic, the S5/S8 EPC bearer IS used for paging procedure asillustrated in the FIG. 15.

The S5/S8 bearer is used for LIPA/SIPTO connection during the ECM-IDLEmode.

The following describes possible enhancements (shown as under-linedcharacters) in the signaling flows of FIG. 16. The enhancements helpovercome the deficiencies outlined above.

Two alternatives are shown that solve the EPC bearer deficiency. Thefirst alternative in the following section (A) proposes that the EPCoptimization takes place when the UE attaches to the EPC. The thefollowing section (B) shows a solution where that the EPC optimizationtakes place after the requested EPC bearers have been established.

In this procedure, the S1 release procedure is used and enhanced for theEPC optimization.

Finally, the following section (C) shows the paging scenario and how theoptimized EPC bearers are re-established.

(A) S5/S8 Optimization Alternative 1 (at the Initial ATTACH Procedure)

The general signaling flows for the initial ATTACH procedure in case theLP-GW is collocated or logically very close to the eNB will now bedescribed.

For the GBR connection, the Non-GBR bearer is established over the S5/S8interface and no bearer is established over the S1 interface. The(small) enhancements are listed below.

The eNB informs the MME about LIPA/SIPTO configuration by means of theS1SUP procedure and/or the ATTACH request/TA update procedures. Based onthis information, MME can make a decision whether S1 bearer and S5/S8bearer would be used or not. In FIG. 16, MME, responsive to an ATTACHrequest, HeNB attaches connection related information to the ATTACHrequest and sends the the ATTACH request to the MME (2 in FIG. 16). Theuser authentication (User Authentication) is then carried out (3 of FIG.16). Based on the information available, the MME decides on whether ornot S1 or GBR S5/S8 is necessary. In this case, these are not necessarybecause the configuration is that of LIPA.

If the MME decides that, due to the LIPA/SISTO connection, the S5/S8bearer is not used, the MME sends a create session request (CreateSession Request) ( . . . S5/S8 to be Non-GBR)) to the S-GW (5 of FIG.16). This create session request indicates that a non-GBR bearer(Non-GBR) is to be established for the S5/S8 interface.

In this case, the MME maintains the original GBR attributes (designatedGBR attributes) so that the original GBR bearer as requested will beable to be subsequently established on the S5/S8 interface (5 of FIG.16).

The S-GW requests the LP-GW to set up a non-GBR bearer for S5/S8interface (Create Session Request ( . . . , S5/S8 to be Non-GBR)) (7 ofFIG. 16). The LP/GW assigns non-GBR bearer attributes (8 of FIG. 16:Assign Non-GBR bearer attributes). The LP-GW returns a response (CreateSession Response) to the S-GW (7 of FIG. 16) and the S-GW returns aresponse (Create Session Response) to the MME (5 of FIG. 16).

If the MME decides that the S1 bearer is not used due to the LIPA/SISTOconnection, the MME sends an initial context setup message indicatingthat the S1 bearer is not to be established (Initial contextsetup/Attach Accept ( ) . . . , No S1 bearer) to the HeNB (9 of FIG.16). Thus, no resources are assigned to the S1 bearer (11 of FIG. 16).

(B) S5/S8 Optimization Alternative 2 (Triggered by S1 Release Procedure)

The following describes the general signaling flows for the S1 releaseprocedure with S5/S8 optimization. According to the present invention,there is proposed that all necessary bearers are established once andrelying on the S1 release procedure for the EPC optimization.

FIG. 17 illustrates a situation where the eNodeB decides to initiate anS1 releasing procedure (S1 UE Context Release Request) due to LIPA/SISTOconnection. In FIG. 17, the passages shown underlined correspond to theenhancements by the present invention.

On receiving an S1 UE context release message (1 of FIG. 17: S1 UEContext Release Request) from the HeNB, the MME is able to decide, basedon the information available and on the operator policy, whether or notto S5/S8 is to be optimized. Since the connection is LIPA, S5/S8 isoptimized.

If the MME decides that, since the connection is LIPA/SIPTO, the S5/S8bearer is to be optimized, the MME sends a release access bearer request(3 of FIG. 17: Release access bearer Request ( . . . , S5/S8 to beNon-GBR)) to the S-GW. The S-GW sends to the LP-GW a modify bearerrequest (Modify Bearer request) ( . . . , S5/S8 to be Non-GBR) thatindicates that a non-GBR bearer is to be established for the S5/S8interface (4 of FIG. 17). The LP-GW releases the GBR related resourcesof S5/S8 (5 of FIG. 17). The LP-GW returns a modify bearer response(Modify Bearer Response) to the S-GW (4 of FIG. 17), in response towhich the S-GW releases the GBR related resources to return to the MME arelease access bearers response (Release Access Bearers Response) (3 ofFIG. 17).

On receiving from the MME a UE context release command message (9 ofFIG. 17: UE Context release command), the HeNB does not release theradio bearer (10 of FIG. 17). The reason is that the HeNB knows that theUE context release procedure has been initiated because of theLIPA/SISTO connection. Otherwise, the radio bearer is released. The HeNBnotifies the MME of the completion of the UE context release (9 of FIG.17: UE Context release complete).

According to the present invention, the following points of enhancementmay bring a lot of benefits for the 3G operator. The reason is that theproposed points of enhancement may optimize EPC resource assignment tohelp the operator to minimize network costs.

The S1/lu bearer resources may be removed/diminished for LIPA/SIPTOtraffic. This is possible since all LIPA/SIPTO traffic that is brokenout locally does not traverse the S1/lu bearer and hence is not in needof any bearer resources.

When the GBR bearer is used for LIPA/SIPTO connection, the S5/S8 orGn/Gp bearer may also be optimized by downgrading it to a Non-GBRbearer. For example, if it has become necessary for the UE to set upnon-LIPA/SIPTO connection due to idle mode mobility to non-LIPA/SIPTOmacro eNodeB, the GBR bearer is re-established on the S5/S8 or Gn/Gpreference point. The S5/S8 or Gn/Gp bearer may not be removed in thesame way as the S1/lu bearer since these bearers may also be used for aDL (Down Link) packet arrival while the UE is in the ECM-IDLE mode.

FIG. 18 shows a signaling flow for a GBR bearer re-establishmentprocedure in case a DL (Down Link) packet has arrived. Referring to FIG.18, the passages shown underlined corresponds to the enhancements.

A DL packet arrives at S-GW from LP-GW via a non-GBR bearer (1 of FIG.18). The S-GW sends to the MME a DL data notification request (DownlinkData Notification request) (2 of FIG. 18). The MME causes the eNodeB toperform the paging (3 of FIG. 18). The eNodeB sends a service request tothe UE (4 of FIG. 18). The MME sends a context setup request (UE Contextsetup request) to the eNodeB (5 of FIG. 18) so that a radio bearer willbe established between the UE and the eNodeB (6 of FIG. 18). The eNodeBthen notifies the MME of the completion of UE context setup (UE Contextsetup response) (5 of FIG. 18).

The MME sends to the S-GW a modify bearer request (Modify Bearer request( . . . , S5/S8 to be the GBR)), which modifies S5/S8 into a GBR bearer(7 of FIG. 18). The S-GW sends to the LP-GW a modify bearer request(Modify Bearer request) ( . . . , S5/S8 to be the GBR)) (8 of FIG. 18).The LP-GW assigns GBR resources to S5/S8 (9 of FIG. 18) to send a modifybearer response (Modify Bearer response) to the S-GW (8 of FIG. 18). TheS-GW assigns GBR resources to S5/S8 (10 of FIG. 18) and sends a modifybearer response to the MME (7 of FIG. 18). As a result, the EPC bearerconfiguration includes a S5/S8 bearer (GBR), S1 bearer (GBR) and a radiobearer.

The above mentioned enhancements are proposed to be captured in TR23.8xy(Local IP Access and Selected IP Traffic Offload).

The solutions for the local IP access (LIPA) for the Home (e)NodeBsubsystem and selected IP traffic offload (SIPTO) shall fulfill theservice requirements described in TS22.220.

The solutions for the SIPTO for the Home (e)NodeB subsystem shallsatisfy service requirements described in 3GPP TS 22.101.

The solutions for the SIPTO for the macro (3G and LTE) shall fulfill thefollowing architectural requirements:

-   -   It shall be possible to perform traffic offload without user        interaction.    -   For UTRAN, the traffic offloading shall be performed on or above        an RNC node.    -   The impact on the existing network entities and procedures by        introducing traffic offload shall be minimized.

The H(e)NBs supporting LIPA shall be able to provide Intranet typeaccess to the home based network.

It should be noted that if the home based network provides a route toother private networks or to the public internet, then these networksmay be accessible via LIPA.

Resource allocations in the EPC for LIPA/SIPTO traffic shall beminimized: It shall be possible not to establish the S1/Iu bearer forthe LIPA/SIPTO traffic that has been broken out locally in the macro orhome (e)NB.

-   -   If a GBR bearer is used for the LIPA/SIPTO connections, it shall        be possible to optimize the S5/S8 or Gn/Gp bearer by reducing        the allocated resources or downgrading it to a Non-GBR bearer.

The full GBR bearer resources over the S5/S8 or Gn/Gp reference pointsshall be re-established once the LIPA/SIPTO traffic is not broken outlocally anymore, for example, in case of idle mode mobility to a macrocell.

Following listed are terms and definitions used in the presentspecification, in which the left terms and right terms in the equationshave the same meaning.

-   LIPA/SIPTO connection=LIPA/SIPTO service-   S5/S8 interface=S5/S8 reference point-   eNB=eNodeB=enhanced Node B-   H(e)NB=Home(e) Node B=Home Node B and Home enhanced Node B-   HeNB=Home enhanced Node B-   page=paging=paging procedure    The particular exemplary embodiments or examples may be modified or    adjusted within the gamut of the entire disclosure of the present    invention, inclusive of claims, based on the fundamental technical    concept of the invention. Further, a variety of combinations or    selection of elements disclosed herein may be made within the    framework of the claims. That is, the present invention may cover a    wide variety of modifications or corrections that may occur to those    skilled in the art in accordance with the entire disclosure of the    present invention, inclusive of claim and the technical concept of    the present invention.

What is claimed is:
 1. A method for a mobile communication system, themethod comprising: releasing, by an MME (Mobility Management Entity),bearers in an SGW (Serving Gateway) by sending a request to the SGW whenSIPTO (Selected IP Traffic Offload) is established; and sending, by theSGW, a response to the MME.
 2. A mobile communication system, the systemcomprising: an MME (Mobility Management Entity); and an SGW (ServingGateway), wherein the MME releases bearers in the SGW by sending arequest to the SGW when SIPTO (Selected IP Traffic Offload) isestablished, and wherein the SGW sends a response to the MME.
 3. Amobility management node used in a mobile communication system, the nodecomprising: a unit that sends a request to an SGW (Serving Gateway) forreleasing bearers in the SGW when SIPTO (Selected IP Traffic Offload) isestablished; and a unit that receives a response from the SGW.
 4. Themobility management node according to claim 3, wherein the mobilitymanagement node comprises an MME (Mobility Management Entity).
 5. Amethod for a mobility management node used in a mobile communicationsystem, the method comprising: sending a request to an SGW (ServingGateway) to release bearers in the SGW when SIPTO (Selected IP TrafficOffload) is established; and receiving a response from the SGW.
 6. Themethod according to claim 5, wherein the mobility management nodecomprises an MME (Mobility Management Entity).